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      In vivo wear of CAD-CAM composite versus lithium disilicate full coverage first-molar restorations: a pilot study over 2 years

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          Abstract

          Objectives

          To present a digital approach to measure and compare material wear behavior of antagonistic first molar restorations made of an experimental CAD/CAM composite (COMP) and lithium disilicate ceramic (LS2) in patients with reconstructed vertical dimension of occlusion (VDO) after generalized hard tissue loss.

          Methods

          A total of 12 patients underwent complete full jaw rehabilitation with full occlusal coverage restorations made either of COMP or LS2. The first molar restorations ( n = 48) were chosen for wear examination. At annual recall appointments, polyether impressions were taken, and resulting plaster casts were digitalized using a laboratory scanner. Mean observation period was 371 days for first and 769 days for second year. The resulting 96 datasets were analyzed by superimposition of 3-D datasets using an iterative best-fit method. Based on the superimposition data, the wear rates of the occlusal contact areas (OCAs) were calculated.

          Results

          For antagonistic restorations made of COMP, the average wear rate was 24.8 ± 13.3 μm/month, while for LS2, it was 9.5 ± 4.3 μm/month in first year, with significant differences ( p < 0.0001) between the materials. In second year, monthly wear rates decreased significantly for both materials: COMP (16.2 ± 10.7 μm/month) and LS2 (5.5 ± 3.3 μm/month). Statistical comparison between wear time showed significant differences for both materials: COMP p < 0.037 and LS2 p < 0.001. A logarithmic fit (COMP R 2 = 0.081; LS2 R 2 = 0.038) of the data was calculated to estimate the wear progression.

          Significance

          In patients with reconstructed VDO, restorations made of LS2 show a more stable wear behavior than ones out of experimental CAD/CAM composite. In cases of complete rehabilitation, load bearing CAD/CAM-composite restorations should be critically considered for application due to their occlusal wear behavior. However, when choosing a restorative material, not only the functional occlusal stability should be taken into account but also the prospect of minimally invasive treatment with maximum preservation of natural tooth structures.

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          Most cited references48

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          In vivo precision of conventional and digital methods of obtaining complete-arch dental impressions.

          Digital impression systems have undergone significant development in recent years, but few studies have investigated the accuracy of the technique in vivo, particularly compared with conventional impression techniques.
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            Erosive tooth wear: a multifactorial condition of growing concern and increasing knowledge.

            Dental erosion is often described solely as a surface phenomenon, unlike caries where it has been established that the destructive effects involve both the surface and the subsurface region. However, besides removal of the surface, erosion shows dissolution of mineral within the softened layer - beneath the surface. In order to distinguish this process from the carious process it is now called 'near surface demineralization'. Erosion occurs in low pH, but there is no fixed critical pH value concerning dental erosion. The critical pH value for enamel concerning caries (pH 5.5-5.7) has to be calculated from calcium and phosphate concentrations of plaque fluid. In the context of dental erosion, the critical pH value is calculated from the calcium and phosphate concentrations in the erosive solution itself. Thus, critical pH for enamel with regard to erosion will vary according to the erosive solution. Erosive tooth wear is becoming increasingly significant in the management of the long-term health of the dentition. What is considered as an acceptable amount of wear is dependent on the anticipated lifespan of the dentition and is, therefore, different for deciduous compared to permanent teeth. However, erosive damage to the teeth may compromise the patient's dentition for their entire lifetime and may require repeated and increasingly complex and expensive restorations. Therefore, it is important that diagnosis of the tooth wear process in children and adults is made early and that adequate preventive measures are undertaken. These measures can only be initiated when the risk factors are known and interactions between them are present.
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              From Artisanal to CAD-CAM Blocks: State of the Art of Indirect Composites.

              Indirect composites have been undergoing an impressive evolution over the last few years. Specifically, recent developments in computer-aided design-computer-aided manufacturing (CAD-CAM) blocks have been associated with new polymerization modes, innovative microstructures, and different compositions. All these recent breakthroughs have introduced important gaps among the properties of the different materials. This critical state-of-the-art review analyzes the strengths and weaknesses of the different varieties of CAD-CAM composite materials, especially as compared with direct and artisanal indirect composites. Indeed, new polymerization modes used for CAD-CAM blocks-especially high temperature (HT) and, most of all, high temperature-high pressure (HT-HP)-are shown to significantly increase the degree of conversion in comparison with light-cured composites. Industrial processes also allow for the augmentation of the filler content and for the realization of more homogeneous structures with fewer flaws. In addition, due to their increased degree of conversion and their different monomer composition, some CAD-CAM blocks are more advantageous in terms of toxicity and monomer release. Finally, materials with a polymer-infiltrated ceramic network (PICN) microstructure exhibit higher flexural strength and a more favorable elasticity modulus than materials with a dispersed filler microstructure. Consequently, some high-performance composite CAD-CAM blocks-particularly experimental PICNs-can now rival glass-ceramics, such as lithium-disilicate glass-ceramics, for use as bonded partial restorations and crowns on natural teeth and implants. Being able to be manufactured in very low thicknesses, they offer the possibility of developing innovative minimally invasive treatment strategies, such as "no prep" treatment of worn dentition. Current issues are related to the study of bonding and wear properties of the different varieties of CAD-CAM composites. There is also a crucial need to conduct clinical studies. Last, manufacturers should provide more complete information regarding their product polymerization process, microstructure, and composition, which significantly influence CAD-CAM material properties.
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                Author and article information

                Contributors
                jan_frederik.gueth@med.uni-muenchen.de
                kurt.erdelt@med.uni-muenchen.de
                christine.keul@med.uni-muenchen.de
                gintare.burian@med.uni-muenchen.de
                josef.schweiger@med.uni-muenchen.de
                daniel.edelhoff@med.uni-muenchen.de
                Journal
                Clin Oral Investig
                Clin Oral Investig
                Clinical Oral Investigations
                Springer Berlin Heidelberg (Berlin/Heidelberg )
                1432-6981
                1436-3771
                12 May 2020
                12 May 2020
                2020
                : 24
                : 12
                : 4301-4311
                Affiliations
                GRID grid.5252.0, ISNI 0000 0004 1936 973X, Department of Prosthetic Dentistry, University Hospital, , LMU Munich, ; Goethestrasse 70, 80336 Munich, Germany
                Article
                3294
                10.1007/s00784-020-03294-5
                7666668
                32399736
                62efa2c7-4c39-464e-8298-2327c2dab410
                © The Author(s) 2020

                Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

                History
                : 19 August 2019
                : 17 April 2020
                Funding
                Funded by: Ivoclar Vivadent
                Categories
                Original Article
                Custom metadata
                © Springer-Verlag GmbH Germany, part of Springer Nature 2020

                Dentistry
                abrasion,wear,dental materials,cad/cam composite,lithium disilicate,wear behavior
                Dentistry
                abrasion, wear, dental materials, cad/cam composite, lithium disilicate, wear behavior

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